全文获取类型
收费全文 | 1711篇 |
免费 | 37篇 |
国内免费 | 3篇 |
专业分类
化学 | 709篇 |
晶体学 | 13篇 |
力学 | 58篇 |
数学 | 139篇 |
物理学 | 617篇 |
无线电 | 215篇 |
出版年
2022年 | 22篇 |
2021年 | 19篇 |
2020年 | 27篇 |
2019年 | 21篇 |
2018年 | 25篇 |
2017年 | 36篇 |
2016年 | 42篇 |
2015年 | 25篇 |
2014年 | 46篇 |
2013年 | 102篇 |
2012年 | 85篇 |
2011年 | 95篇 |
2010年 | 66篇 |
2009年 | 65篇 |
2008年 | 86篇 |
2007年 | 74篇 |
2006年 | 51篇 |
2005年 | 68篇 |
2004年 | 51篇 |
2003年 | 46篇 |
2002年 | 49篇 |
2001年 | 29篇 |
2000年 | 32篇 |
1999年 | 34篇 |
1998年 | 19篇 |
1997年 | 22篇 |
1996年 | 22篇 |
1995年 | 17篇 |
1994年 | 25篇 |
1993年 | 32篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 20篇 |
1989年 | 25篇 |
1988年 | 18篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1978年 | 23篇 |
1977年 | 11篇 |
1976年 | 18篇 |
1975年 | 15篇 |
1974年 | 15篇 |
1973年 | 12篇 |
排序方式: 共有1751条查询结果,搜索用时 15 毫秒
11.
Heavy ion irradiation in the electronic stopping power region induces macroscopic dimensional change in metallic glasses and introduces magnetic anisotropy in some magnetic materials. The present work is on the irradiation study of ferromagnetic metallic glasses, where both dimensional change and modification of magnetic anisotropy are expected. Magnetic anisotropy was measured using Mössbauer spectroscopy of virgin and irradiated Fe40Ni40B20 and Fe40Ni38Mo4B18 metallic glass ribbons. 90 MeV 127I beam was used for the irradiations. Irradiation doses were 5×1013 and 7.5×1013 ions/cm2. The relative intensity ratios D 23 of the second and third lines of the Mössbauer spectra were measured to determine the magnetic anisotropy. The virgin samples of both the materials display in-plane magnetic anisotropy, i.e., the spins are oriented parallel to the ribbon plane. Irradiation is found to cause reduction in magnetic anisotropy. Near-complete randomization of magnetic moments is observed at high irradiation doses. Correlation is found between the residual stresses introduced by ion irradiation and the change in magnetic anisotropy. 相似文献
12.
13.
We develop a new joint cure rate model for longitudinal and survival data. The model allows for multiple longitudinal markers as well as a cure structure for the survival component based on the promotion time cure rate model, as described in Ibrahim et al. (Bayesian Survival Analysis, Springer, New York, 2001). Several characteristics and properties of the new model are discussed and examined. A real dataset from a melanoma clinical trial is given to demonstrate the methodology. 相似文献
14.
Zaleski A. Sinha S.P. Ioannou D.E. Campisi G.J. Hughes H.L. 《Electron Devices, IEEE Transactions on》1995,42(9):1697-1700
By operating one channel of a typical SOI MOSFET in avalanche while keeping the opposite channel accumulated, charge injection into the opposite gate takes place. Three independent experiments are described that demonstrate the occurrence of this opposite-channel based charge injection. The experimental results are in agreement with PISCES numerical simulations 相似文献
15.
M K Parida Nita Sinha B Adhikary B Allanach A Alok K S Babu B Brahmachari D Choudhury E J Chun P K Das A Ghosal D Hitlin W S Hou S Kumar H N Li E Ma S K Majee G Majumdar B Mishra G Mohanty S Nandi H Pas M K Parida S D Rindani J P Saha N Sahu Y Sakai S Sen C Sharma C D Sharma S Shalgar N N Singh S Uma Sankar N Sinha R Sinha F Simonetto R Srikanth R Vaidya 《Pramana》2006,67(5):849-860
This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been
mainly focused on B-physics, those in model building have been primarily devoted to neutrino physics. We present summary of working group discussions
carried out during the workshop in the above fields, and also briefly review the progress made in some projects subsequently. 相似文献
16.
A layer of stratified combination composed of selected radiation shielding materials acquires better shielding property. Albedo
is used in such measurements as an integral measure ofγ-ray scattering. The stratified slabs of alternating heterogeneous layers have been found to have a virtual homogeneous property
with a definite effective atomic number. The angular distribution of back-scattered photons as well as the total number albedo
values for iron, aluminium and concrete in stratified combination for 662 keV and 1250 keV photons are reported. 相似文献
17.
D. Seweryniak P. J. Woods B. Blank M. P. Carpenter T. Davinson S. J. Freeman J. Grres A. Heinz R. V. F. Janssens H. Mahmud T. L. Khoo Z. Liu G. Mukherjee E. Rehm F. Sarazin J. Shergur M. Shawcross S. Sinha A. Woehr 《Physics letters. [Part B]》2004,590(3-4):170-175
The fusion–evaporation reaction 10B(12C, 2n) was used to make the first observation of in-beam γ decays from the astrophysically important nucleus 20Na, lying adjacent to the proton drip-line. All states below the proton threshold in 20Na were populated and identified in the experiment. These include new levels, previously unresolved levels, and states located with improved energy precision. The level structure of 20Na, and its γ transitions, are compared to the mirror partner 20F measured simultaneously in this experiment. In particular, a high degree of energy stability is found for all negative parity states. These results are discussed in the context of the nuclear shell model. 相似文献
18.
The complete proofs of Krein’s theorem on the spectral shift function and the trace formula are given for a pair of self-adjoint
operators such that either (i) their difference is trace-class or (ii) the difference of their resolvents is trace-class.
The proofs, essentially due to Krein, is based on Herglotz’s theorem on the boundary value of the analytic functions whose
imaginary part is non-negative on the upper half plane, and an almost optimal class of functions are obtained for which the
trace formula is valid. Also an alternative method based on Weyl-von Neumann’s theorem for self-adjoint operators, avoiding
the complex function theory and inspired by Voiculescu’s work, is given for the first case. Furthermore, some applications
of the spectral shift function have been discussed. 相似文献
19.
20.
D. Sinha G.K. Sarker S. Ghosh A. Kulshreshtha K.K. Dwivedi D. Fink 《Radiation measurements》1998,29(6):599-604
Photon induced modifications in Triafol-TN and Triafol-BN polymers have been studied in the dose range of 101–106 Gy at room temperature using a 60Co source. To monitor the chemical and structural changes induced by gamma rays, UV, IR, and ESR studies were carried out. Thermal studies were also conducted for understanding the effects of gamma irradiations on these polymers. Variation of track etching characteristics and activation energy for bulk etching have been studied at different gamma rays doses. The experimental results are presented and discussed. 相似文献